Heat-developable two-component diazotype reproduction material



United States Patent Ofilice 3,360,371 Patented Dec. 26, 1967 3,360,371HEAT-DEVELOPABLE TWO-COMPONENT DIAZO- TYPE REPRODUCTION MATERIALJohannes Munder, Wiesbaden-Biebrich, and Hellmut Ziegler,Wiesbaden-Schierstein, Germany, assignors, by mesne assignments, toKeulfel & Esser Company, Hoboken, NJ.

No Drawing. Filed Dec. 27, 1963, Ser. No. 334,029 Claims priority,application Germany, Dec. 29, 1962, K 48,608 9 Claims. (Cl. 96-91) Thepresent invention relates to diazotype reproduction materials and refersmore particularly to heat-developable two-component diazotypereproduction materials and methods for their preparation.

In the preparation of copies by means of the diazotype procedure, threemethods of development are used: the dry process using ammonia, thesemi-wet process, and the thermal process. Copies are obtained byexposing the light-sensitive material behind a master to destroy thediazo compound in the image-free area but not in the image areas. Theundestroyed diazo compound together with the coupling component alreadypresent or added by developer bat-h then forms an azo dyestuff under theproper pH conditions. This is accomplished by shifting the pH value froman acid to an alkaline value in the case of the dry process, by heatingin the case of the thermal process, or by applying the couplingcomponent in a pH- controlled developer solution in the case of thesemi-wet process.

The coupling process proceeds without difficulties only if it iseffected in the alkaline to neutral pH range. Thus, in most of theheat-developing processes hitherto known, the original acid pH value ofthe light-sensitive layer was shifted from acid to neutral to alkalinevalues as the temperature was increased by the presence of suitableadditives. This effect was obtained by using a solid acid easilyvolatilized by heat or a non-alkaline substance which is transformed byheat to an alkaline substance. Urea is generally used for this purposesince it has a neutral reaction at room temperature whereas it isdecomposed to biuret and ammonia at 150 to 160 C.

Urea-containing papers, however, have the disadvantage that they arehygroscopic and thus are subject to undesirable pre-coupling due to thepresence of absorbed moisture. Furthermore, the decompositiontemperature of urea is high. Thus, susceptible diazo compounds start todecompose appreciably and the water necessary for the coupling reactionescapes from the paper, thus markedly lessening the contrast. Inaddition, the reproduction material used for diazotype purposes developsunpleasant vapors when heated strongly and the guide rollers of thereproduction apparatus become contaminated with decomposition productsfrom the copying material when used for long periods of time.

The present invention relates to a heat-developable twocomponentdiazotype reproduction material which contains in the light sensitivelayer: a diazo compound, an azo compound, and a component which underthe influence of heat increases the pH-value in the layer and thuspermits coupling to occur. It is characterized by the fact that thecomponent or developing agent consists of a substance which is alkalinein aqueous medium, and is present in the form of small particles whichare individually enveloped by an organic substance insoluble in waterand melting between 50 and 200 C.

Therefore, one object of the present invention is to provide aheat-developable two-component diazotype reproduction material utilizingan alkaline developing agent in the form of small enveloped particles.

Another object is to provide a heat-developable twocomponent diazotypereproduction material which has good keeping and good contrast.

Another object is to provide methods for making a heat-developabletwo-component diazotype reproduction material.

Other objects will become apparent during the course of thespecification.

For the preparation of the enveloped alkaline substances, the finelydivided substance is introduced into a melt of a suitable wax or resin,substantially homogenized, solidified, pulverized and washed with asolvent, preferably a diluted acid, to remove any alkaline nonenvelopedmaterial adhering to the particles.

Another process for the production of the finely divided envelopedalkaline material comprises distributing a finely divided base in asolution of an organic water-insoluble substance melting between and 200C. so that a uniform dispersion is obtained, spraying the latter anddrying the spray and, if necessary, washing the fine powder thusobtained with dilute acid in order to remove any nonenveloped basicmaterial adhering to the particles.

Spraying and drying of the dispersion can be effected in a large uprightchute into which the dispersion is injected through a nozzle from thetop and a stream of heated air or gas is passed upward to meet thefalling sprayed droplets. The hot gas stream rapidly evaporates thesolvent from the droplets so that the dispersed material falls to thebottom as a fine dust. According to another process for spray drying,the dispersion is caused to drip in a closed container onto a spray discwhich is rotated at high speed, e.g., 5,000 to 20,000 revolutions perminute, whereby the liquid is atomized. The sprayed particles are driedby means of a heated gas stream passed through the container to producea fine powder. These processes can be varied in numerous ways. Thus, thespray drying can be effected in an ambient atmosphere of very highpressure. The heated gas can be passed down together with the dispersionto be dried instead of being passed countercurrently.

For practical purposes the finely divided enveloped basic particlesaccording to the present invention are preferably used up to a grainsize of 30 microns. When a coarser powder is used it is difficult toobtain a uniformly coated diazotype reproduction material. Theseparation of the fraction having the desired particle size is effectedby screening or wind sifting. Under suitable conditions, envelopedparticles of 30 microns and less can be obtained directly by spraydrying.

As suitable bases of the present invention, all substances which areinsoluble in the wax or resin used as enveloping material and in thesolvent used for the spraying process can be used. Bases which are onlyslightly soluble in water are preferred, since very thin films of wax orresin with slight permeability to water can burst open due to osmoticpressure when suspended in water if the enclosed substances are tooreadily soluble in water. The following are mentioned as examples forsuitable bases which are only slightly soluble in water: oxides andhydroxides of the elements of the second and third group of the PeriodicSystem, preferably those of the alkaline earth metals, of cadmium,aluminum, zinc and the rare earths; and the salts of these bases withweak acids such as carbonic acid, boric acid,,acetic acid, citric acid,and salicylic acid. When relatively water impermeable substances such asvinylidene chloride-vinyl chloride copolymers are used for theenvelopes, derivatives of the alkaline metals such as sodium tetraboratemay also be used. Furthermore, organic bases such astriethylammonium-carbonate as well as tri-tertiary-butylamine,triisopropylamine, triethylamine and the salts thereof with weak organicacids are suitable.

Suitable films for enveloping the basic substance are those which arewater insoluble, melt between 50 and 200 C., are colorless or onlyweakly colored in a thin layer, are relatively fluid in molten form andsufficiently hard and brittle at room temperature and can be finelydivided, and which do not react with other substances also used for thecoating. For instance, wax-like or resinous substances having theseproperties can be used. They include natural resins such a colophony,root resin and shellac; conversion products of natural resins such ashydrogenated resins, hardened rosins and zinc resins, resin esters andsynthetic resins modified with natural resins; maleinate resins;oil-free alkyd resins; light-colored phenolic resins of the novolactype; alkyl phenolic resins and terpene phenolic resins; coumaroneresins; vinyl polymers such as polyvinyl acetals, polyvinyl acetates,polyvinyl chloride, polyvinylidene chloride, polyvinyl ether,polyacrylic ester, polystyrene and copolymers of the vinyl compoundswith each other and with other polymerizable compounds; polymers ofaliphatic unsaturated hydrocarbons; ketone resins; chlorodiphenylresins; epoxy resins and silicone resins. Substances with a low meltingpoint within the above range should preferably have a narrow meltingrange of not more than 10 C.

All compounds conventionally used in diazotype processes can be employedas the azo coupling component provided they can couple under theinfluence of heat in the alkaline or neutral pI-I-range with suitablediazo compounds to produce a dyestutf and provided that they do notreact with the resin or wax used for enveloping the base. Compounds ofpoor solubility in water are similarly preferred and they can also bepresent in the form of finely divided material enveloped by a film oforganic material. Furthermore, it is advantageous that the melting pointof the coupling component be within or below the melting range of theresin or wax. Some examples are: 2,3-dihydroxynaphth-alene; aceto aceticanilide; 2,3-dihydroxynaphthalene-6-sulfonic acid sodium salt;2-naphthol- 3-carboxylic acid methyl ester; 3,5-dihydroxybenzic acid;2,4-dihydroxy-benzamide; l-methyl-3-hydroxy-benzene-4- glutaric iacid;phenol-B-urea; 2-naphth0l 3,6 disulfonic acid sodium salt.

Diazo compounds which are sufficiently stable in the temperature rangeof the heat-development, couple with the azo coupling component inalkaline or neutral pH range under the influence of heat to form adyestuff, and do not react with the resin or wax used for enveloping thebasic substance or the azo coupling component can be used. Examples ofsuch compounds are: 2,5-diethoxy-4- benzoylamino-benzene diazoniumchloride; 4-phenylamino-benzene diazonium hydrogen sulfate;4-diazo-2,5-dimethoxy 4' methyl-diphenylsulfide (HCl salt); 4morpholincrbenzene diazonium fluoborate; 4-morpholino-2,5-diethoxybenzene diazonium chloride; 4-dimethyl-aminobenzene diazoniumchloride; 4-(4'-ethoxy-phenyl)-2,5-diethoxybenzene diazonium chloride;4-ethylbenzylaminobenzene diazonium chloride;2-ethoxy-4-diethylaminobenzene diazonium chloride; and4-benylamino-2,S-diethoxybenzene diazonium chloride.

The diazotype reproduction material according to the present inventioncan also contain a solid acid such as tartaric or citric acid.Furthermore, additives conventionally used in the diazotype processescan be used. Zinc chloride and thiourea are examples. It is alsoconvenient to add a wetting agent, such as saponine, to effect bettersuspension of the particles. It is also preferable to use a bindingagent such as carboxymethyl cellulose, soluble starch, casein, gelatine,or synthetic resin dispersions to ensure the adhesion of the particleson the carrier material. As sheet-like supports conventional raw paperscan be used. Transparent foils of converted cellulose products such ascellulose hydrate or cellulose esters or of plastics such as polyamides,polyesters, polycarbonates, and polyvinyl compounds can also beemployed. Paper and similar cellulose products are preferably used.

The individual components of the coating are preferably applied to thecarrier material in a one-step process.

When using the reproduction material, it is exposed behind a master andthen developed by heating by contact with a warm body such as a warmroller or plate. The development occurs when the envelope base isliberated as the envelope is melted and changes the pH of the layer,thus permitting the coupling reaction to proceed.

By means of the reproduction material according to the present inventiona heat-image can be obtained by the contact process by placing asuitable master between an infrared source and the reproduction materialin such a way that the image side of the master is in contact with theuncoated side of the reproduction material. During exposure to theinfrared radiation, the image areas of the master are more intenselyheated than the image-free areas. With suitable dosage, this heating issuflicient to melt the water insoluble film enveloping the particles inthe image areas, thus producing a dye image in the reproductionmaterial. The images are fixed by subsequent exposure to destroy diazocompound retained in the image-free areas.

Example By wet grinding with 1500 grams of trichloroethylene, 150 gramsof 2,7-dih-ydroxy-naphthalene were converted into a finely dividedmaterial. Then a solution of 300 grams of a maleinate resin having amelting range from 69 to 77 C., such as Hobimal P 59, in 4,500 grams oftrichloroethylene were added and the total mixture was homogenized bymeans of a high speed mixer (Ultra- Turrax). This mixture was sprayedinto a heated conic vessel, so that solvent was evaporated and resinenveloped the particles of the azo coupling component as a protectivefilm. By wind sifting, the portion with a maximum particle size of 30microns was separated. The powder obtained was designated as powder I.

A 2% aqueous solution of zinc sulfate was adjusted to a pH value of 8 bythe addition of ammonia with vigorous stirring, and the zinc hydroxidethus obtained was separated as a finely divided material by spraydrying. The ammonium sulfate contained in the finely divided dry productwas removed by washing with water and the residue was dried at 60 C.Then 120 grams of the zinc hydroxide were dispersed in a solution of 240grams of a maleinate resin (Hobimal P 59), dissolved in 4,000 grams oftrichloroethylene and atomized as described above. No wind sifting wasnecessary. The powder obtained was designated as powder II.

An aqueous suspension was made up of:

15 grams of powder I 20 grams of powder II 4 grams of4-dimethylamino-benzene diazonium chloride-zinc chloride 0.5 gram oftartaric acid 2 grams of trichloroacetic acid 3 grams ofnaphthalene-1,3,6-trisulfonic acid 8 grams of thiourea 2 grams ofpolyvinyl acetate (Mowilith DV) 0.4 gram of saponine 150 grams of waterand homogenized by means of a high-speed mixer.

The above mentioned resin sold under the trade name Hobimal P 59 is apolyester resin prepared by condensing maleic acid, rosin, and apolyhydric alcohol.

The aqueous suspension was applied to a raw paper and the carriermaterial coated in this way was dried in an air stream at 30 to 40 C.

After exposure to a UV are lamp behind a master, the material obtainedwas developed by short contact with plates heated to a temperature of toC. A blue copy corresponding to the master was thus obtained.

It is apparent that the described example is capable of many variationsand modifications within the scope of the present invention. All suchvariations and modifications are to be included within the scope of thepresent invention.

What is claimed is:

1. A heat-developable two-component diazotype reproduction materialcomprising a sheet-like support and a light-sensitive layer coated onsaid support, said layer comprising diazo compound, coupler and a finelydivided heat-activatable alkaline developing agent, said agentconsisting essentially of dry solid particles of low water solubilityinorganic alkali enveloped by .a water-insoluble organic substancemelting between about 50 and 200 C.

2. A material in accordance with claim 1 in which said diazo compound isselected from the group consisting of:2,5-diethoxy-4-benzoylamino-benzene diazonium chloride;4-phenylamino-benzene diazonium hydrogen sulfate;4-diazo-2,5-dimethoxy-4'-methyl-dipheny1 sulfide (HCl-salt);4-m0rph01in0 benene diazonium fluoborate;4-morpholino-2,S-diethoxy-benzene diazonium chloride; 4dimethylamino-benzene diazonium chloride;4-(4'-ethoxy-phenyl)-2,5-diethoxy-benzene diazonium chloride;4-:ethylbenzylamino-benzene diazonium chloride;2-ethoxy-4-diethylamino-benzene diazonium chloride; and 4-benzylamino-2,5-diethoxy-benzene diazonium chloride.

3. A material in accordance with claim 1 in which said coupler is amember selected from the group consisting of: 2,3-dihydroxy-naphthalene;acetoacetic anilide; 2,3-dihydroxy-naphthalene-6-sulfonic acid, sodiumsalt; 2-naphthol-3-carboxylic acid methyl ester; 3,5-dihydroxy-benzoicacid; 2,4adihydroxy-benzamide; 1-methy1-3-hydroxy-benzene-4-glutaricacid; phenol-3-urea; 2-naphthol-3,6-disulfonic acid, sodium salt; and2,7-dihydroxy-naphthalene.

4. A material in accordance with claim 1 in which said diazo compound is4-dimethylamino-benzene diazonium chloride zinc chloride salt, saidcoupler is 2,7-dihydroxynaphthalene, said alkali is zinc hydroxide andsaid substance is a polyester resin condensate of maleic acid, rosin,and a polyhydric alcohol melting between 69 C. and 77 C.

5. A heat-developable two-component diazotype reproduction materialaccording to claim 1 wherein said coupler is in the form of particlesenveloped separately from said alkali by a water-insoulble organicsubstance melting between about 50 C. and 200 C.

6. A material in accordance with claim 5 in which said diazo compound isa member selected from the group consisting of:2,5-diethoxy-4-benzoylamino-benzene diazonium chloride;4-phenylamino-benzene-diazonium hydrogen sulfate;4-diazo-2,S-dimethoxy-4-methyl-diphenyl sulfide (HCl-salt);4-morpholino-benzene diazonium fluoborate; 4-morpholino 2,5diethoxy-benzene diazonium chloride; 4-dimethylamino benzene diazoniumchloride; 4-(4'-ethoxyphenyl) 2,5 diethoxy benzene diazonium chloride; 4ethylbenzylamino benzene diazonium chloride;2-ethox'y-4-diethylamino-benzene diazonium chloride; and4-benzylamino-2,S-diethoxy-benzene diazonium chloride.

7. A material in accordance with claim 5 in which said coupler is amember selected from the group consisting of: 2,3-dihydroxy-naphthalene;acetoacetic anilide; 2,3-dihydroxy-naphthalene-6-sulfonic acid, sodiumsalt; 2-naphthol-3-carboxylic acid methyl ester; 3,5-dihydroxy-benzoicacid; 2,4-dihydroxy-benzamide; 1-methyl-3-hydroxy-benzen'e-4 glutaricacid; phenol-B-urea, 2-naphthol-3,6-disu lfonic acid, sodium salt; and2,7-dihydroxynaphthalene.

8. A material in accordance with claim 5 in which said diazo compound is4-dimethylamino-benzene diazonium chloride zinc chloride salt, saidcoupler is 2,7-dihydroxynaphthalene, said alkali is zinc hydroxide, andsaid substance is a polyester resin condensate of maleic acid, rosin anda polyhydric alcohol melting between 69 C. and 77 C.

9. Material according to claim 1 wherein said inorganic alkali isselected from the group consisting of low water solubility oxides andhydroxides of alkaline earth metals, and weak acid salts of said oxidesand hydroxides.

References Cited UNITED STATES PATENTS 3,016,308 1/1962 Macaulay 963,041,289 6/1962 Katchen et al. 117-36.8 XR 3,111,407 11/1963 Lindquistet a1 -9675 XR 3,113,865 12/1963 Sagura et al 9675 XR 3,173,878 3/1965Reyes 11736. 8 XR 3,202,510 8/1965 Hollmann 9649 XR 3,281,244 10/1966Endermann et al. 9649 XR FOREIGN PATENTS 898,668 6/ 1962 Great Britain.905,621 9/1962 Great Britain.

NORMAN G. TORCHIN, Primary Examiner. C. L. BOWERS, Jm, AssistantExaminer.

1. A HEAT-DEVELOPABLE TWO-COMPONENT DIAZOTYPE REPRODUCTION MATERIALCOMPRISING A SHEET-LIKE SUPPORT AND A LIGHT-SENSITIVE LAYER COATED ONSAID SUPPORT, SAID LAYER COMPRISING DIAZO COMPOUND, COUPLER AND A FINELYDIVIDED HEAT-ACTIVATABLE ALKALINE DEVELOPING AGENT, SAID AGENTCONSISTING ESSENTAILLY FO DRY SOLID PARTICLES OF LOW WATER SOLUBILITYINORGANIC ALKALI ENVELOPED BY A WATER-INSOLUBLE ORGANIC SUBSTANCEMELTING BETWEEN ABOUT 50 AND 200*C.